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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3bb67d86755sm9130047f8f.48.2025.08.17.05.50.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 17 Aug 2025 05:50:14 -0700 (PDT) Date: Sun, 17 Aug 2025 13:50:13 +0100 From: David Laight To: Oleg Nesterov Cc: Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Li RongQing , Yu Kuai , Khazhismel Kumykov , Jens Axboe , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v3 2/2] blk-throttle: kill the no longer needed overflow check in calculate_bytes_allowed() Message-ID: <20250817135013.7567dd13@pumpkin> In-Reply-To: <20250815164102.GA13658@redhat.com> References: <20250815164009.GA11676@redhat.com> <20250815164102.GA13658@redhat.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 15 Aug 2025 18:41:02 +0200 Oleg Nesterov wrote: > Now that mul_u64_u64_div_u64() can't crash there is no need to check for > possible overflow in calculate_bytes_allowed(). > > Signed-off-by: Oleg Nesterov > --- > block/blk-throttle.c | 6 ------ > 1 file changed, 6 deletions(-) > > diff --git a/block/blk-throttle.c b/block/blk-throttle.c > index 397b6a410f9e..66339e22cc85 100644 > --- a/block/blk-throttle.c > +++ b/block/blk-throttle.c > @@ -601,12 +601,6 @@ static unsigned int calculate_io_allowed(u32 iops_limit, > > static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed) > { > - /* > - * Can result be wider than 64 bits? > - * We check against 62, not 64, due to ilog2 truncation. > - */ > - if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62) > - return U64_MAX; > return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ); Not directly related, but the two (u64) casts are pointless and can be removed. David > } >